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Abstract: Site-specific hydrogeological parameters are a prerequisite to investigate the migration of radionuclides in groundwater due to leaching from low-level solid radioactive waste disposal facility (SRWDF) site. The leaching event is a low probability event due to all the engineered safety features provided in SRWDF, but the impact assessment, even due to this low probability event of leaching is a regulatory requirement. The present study focuses on SRWDF located in Tarapur, India. Hydrogeological parameters such as radionuclide specific distribution coefficient (Kd), hydraulic conductivity (HC) and porosity are estimated for a watershed area in and around the SRWDF. Values of HC and porosity for soil samples collected from the disposal site are found to be in the range 0.006–0.15 cm/s (average 0.059 cm/s) and 25.64–32.62% (average 29.19%), respectively. Average hydraulic gradient is found to be 0.007. Using the estimated values of hydraulic gradient, porosity and HC in Darcy’s law, groundwater velocity is calculated as 0.13–3.22 m/day. The distribution coefficient of caesium, the most prevalent radionuclide in low-level solid radioactive waste, is estimated to be ranging between 116.73 and 393.54 ml/g. Physical and chemical characteristics of soil like pH, electrical conductivity, organic matter content, moisture content, CaCO3content and effective cation exchange capacity (ECEC) are determined experimentally. Correlation among the estimated parameters is also studied. The Kdof caesium is found to be positively correlated with porosity, ECEC, clay and silt fraction of the soil and negatively correlated to sand fraction. The site-specific parameters estimated in this study would be useful for carrying out the radiological impact assessment (RIA) of the SRWDF at Tarapur through the terrestrial pathway. Research Highlights:

The values of site-specific distribution coefficient (Kd) of the soil samples range from 116.73 to 393.54 ml/g.

Hydrogeological parameters like hydraulic conductivity, porosity, groundwater velocity have been estimated, and the values range from 0.006 to 0.15 cm/s, 25.64 to 32.62% (average 29.19%), 0.13 to 3.22 m/day, respectively.

Physico-chemical properties like pH, electrical conductivity, organic matter content, moisture content, CaCO3content, and effective cation exchange capacity have been estimated.

Correlation among estimated parameters is studied. Site-specific Kdis found to be positively correlated with porosity, effective cation exchange capacity, clay and silt fraction of the soil and negatively correlated to sand fraction.

The mechanisms responsible for flash-boiling injection were investigated. Using an electromagnetic injector developed for this study, propane, methanol and Indolene were heated and injected into a constant-volume vessel. Two regimes of flash-boiling injection were identified. In the first regime, flash-boiling occurs within the injector nozzle without an increase in spray-cone angle. In the second regime, the nozzle exit pressure is sufficiently low that the two-phase compressible mixture created by flash-boiling within the injector nozzle is underexpanded at the nozzle exit and expands externally to increase the spray-cone angle.

This paper deals with the evaluation of parameterization schemes in the WRF model for estimation of mixing height. Numerical experiments were performed using various combinations of parameterization schemes and the results were compared with the mixing height estimated using the radiosonde observations taken by the India Meteorological Department (IMD) at Mangalore site for selected days of the warm and cold season in the years 2004–2007. The results indicate that there is a large variation in the mixing heights estimated by the model using various combinations of parameterization schemes. It was seen that the physics option consisting of Mellor Yamada Janjic (Eta) as the PBL scheme, Monin Obukhov Janjic (Eta) as the surface layer scheme, and Noah land surface model performs reasonably well in reproducing the observed mixing height at this site for both the seasons as compared to the other combinations tested. This study also showed that the choice of the land surface model can have a significant impact on the simulation of mixing height by a prognostic model.

A Lagrangian trajectory model of atmospheric dispersion using the Langevin equation is implemented on a parallel processing computer system, ANUPAM developed at Bhabha Atomic Research Centre, Bombay, India.In the eight-node system with MIMD architecture, a speed-up of 7.22 was achieved using appropriate load balancing between the host node and other nodes. The concentration distribution obtained using the model for two typical cases: (a) high wind shear, low wind speed stable conditions, and (b) low shear, high wind speed unstable conditions, are illustrated with SODAR data as input. [ABSTRACT FROM AUTHOR]